1. Field of the Invention
The present invention relates to an underwater charge coupled device (CCD) camera for visual testing of a reactor cooling system. More particularly, the present invention relates to an underwater CCD camera for visual testing of a reactor cooling system, which includes a casing, a top surface of which has an area two or more times greater than that of a bottom surface thereof to generate natural convection in the casing by thermal gradient between upper and lower parts inside the casing to thereby remove heat generated by the CCD camera through natural cooling, and lead (Pb)-glass windows dually disposed on a front side of the CCD camera to protect a CCD circuit of the CCD camera from radiation exposure and formed with vent holes, through which interior air between the Pb-glass windows circulates in the casing.
2. Description of the Related Art
In nuclear power generation, energy generated by nuclear fission of nuclear fuel in a reactor heats a primary coolant, and heat of the heated primary coolant is transferred to a secondary coolant in a steam generator so that generated steam can rotate a steam turbine, thereby producing electricity through a power generator.
To test integrity of an interior structure, piping, a pressure container, a heat pipe of the steam generator, etc. constituting a reactor cooling system of a nuclear power plant, nondestructive testing is periodically performed pursuant to nuclear power regulations, the American Society of Mechanical Engineers (ASME) code, or the like.
Particularly, the interior structure of the reactor, the nuclear fuel, and a control clement assembly are subjected to periodic visual testing with respect to accessible parts on an inner surface of the pressure container in accordance with requirements of test plans during long term operation of each nuclear power plant. The objective of the visual testing is to test the integrity, e.g., whether elements of the reactor cooling system are separated. whether the nuclear fuel and control element assembly are damaged, etc. and to inspect and remove foreign matter that can accumulate in the reactor.
Referring to FIG. 1, the nuclear fuel arranged in the reactor is provided in a unit of a fuel assembly 100, which includes a plurality of fuel rods 105. Each of the fuel rods 105 includes uranium pellets 120, each of which is coated with a 1 mm thick Zr-alloy cladding tube 110, no that the fuel rods 105 can be protected from external damage and to prevent radiation leaks.
Due to danger associated with radiation exposure, visual testing of the inner structures in the reactor is carried out not directly by a tester, but indirectly by a CCD camera under water. Thus, the CCD camera for indirect visual testing must he operated under radiation exposure and in water having a temperature of about 30-37° C.
In a conventional underwater CCD camera for visual testing of the fuel assembly 100 in the reactor cooling system, a camera casing suffers a temperature increase up to about 70° C. by heat generated from the CCD camera when the CCD camera is operated in the coolant, so that a CCD circuit can be damaged by the heat. Accordingly, for normal operation of the CCD camera, it is necessary to lower the temperature of the casing. Further, to secure quality of digital images by preventing noise relating to radiation exposure, it is necessary to shield the CCD circuit of the CCD camera from radiation exposure.